Method of assembling a dynamoelectric machine



April 6, 1965 L. w. WIGHTMAN METHOD OF ASSEMBLING A DYNAMOELECTBICMAbHINE Original Filed Aug. 26, 1958 2 Sheets-Sheet 1 April 6, 1965 L.w. WIGHTMAN null" ms Amp/4% United States Patent 3,176,380 METHOD OFASSEMBMNG A DYNAMU- ELECTRTC MACHINE Lawrauce W. Wightman, St. Louis,Mo, assigncr to General Electric Company, a corporation of New YorkContinuation of application Ser. No. 757,652, Aug. 26, 1958. Thisapplication Nov. 28, 1961, her. No. 174,329 Claims. (61. 29-1555) Thisinvention relates to dynamoelectric machines, and more particularly toan improved method of assembling such machines. This application is acontinuation of my co-pending application Serial No. 757,652, filedAugust 26, 1958, for the Method of Assembling a Dynamoelectric Machine(now abandoned), which in turn is a continuation-in-part of my originalapplication Serial No. 543,769, filed October 31, 1955 (now abandoned inview of the continuation-impart application Serial No. 757,652).

With a few specialized exceptions, dynamoelectric machines generallyinclude concentrically arranged stationary and rotatable members, calledrespectively the stator and the rotor, with the rotor being separatedfrom the stator by a predetermined radial air gap. Operation of suchmachines is achieved by the establishment of a flux field across the gapbetween the stator and rotor members, and the strength and effectivenessof this field is controlled to a great extent by the size of the airgap. It is therefore most important to have the two membersconcentrically arranged so that during rotation, the air gap will besubstantially constant. In the past, consideraable time and effort hasgenerally been necessary to effect proper centering of the stationaryand rotatable members. Usually, the machine was assembled with themembers approximately in their final positions, and then the rotor wasmoved about until, by trial and error, its centered position wasachieved. While a properly centered dynamoelectric machine can beachieved by such a process, it will be seen that the time factor must ofnecessity be considerable, thus entailing extra expense. It isaccordingly most desirable to curtail the time involved by achievingcentering of the members in a standard simple manner which willeliminate the trial and error approach previously frequently used.

It is, therefore, an object of this invention to provide an improvedmethod of assembling dynamoelectric machines which will incorporate thedesirable features set forth above.

Further objects and advantages of this invention will become apparentand the invention will be better understood .by reference to thefollowing description and the accompanying drawings, and the features ofnovelty which characterize this invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

In carrying out of the objects of my invention in one form thereof, Iprovide a method of assembling a dynamoelectric machine having a stator,a rotor, and a frame or housing assembly rigidly supporting the statorand rotatably supporting the rotor concentrically with the stator. Thefirst step involves the assembly of the rotor and stator in theirpredetermined relationship, with shim means preferably formed ofhardened thermoplastic or other solid, nonmetallic and fluidic materialprovided in the air gap between them to maintain them in concentricity.The stator, rotor, and the housing assembly are then assembled together,and heat is applied to the assembled dynamoelectric machine to fluidizethe shim means and to cause it to be removed in fluid form from the airgap. In this manner, the air gap is automatically provided so that whenthe assembly is completed there 3,175,380 Patented Apr. 6, 1965 can beno question of eccentricity between the rotor and stator members.

In the drawings, FIGURE 1 is a side view, partly broken away and partlyin cross section, illustrating one embodiment of the stator, rotor, andshim members during the first step of the improved method of thisinvention;

FIGURE 2 this invention;

FIGURE 3 is a similar view during the final step of the improved methodof this invention;

FIGURE 4 is a perspective view of the shim means shown in FIGS. 1-3 andused in the improved method of this invention;

FIGURE 5 is an exploded side elevational view, partially in section, ofcertain parts of a dynamoelectric machine during assembly, the viewillustrating another em bodiment of the shim means used in the improvedmethod of this invention;

FIGURE 6 is an end view, stator shown in FIG. 5; and

FIGURE 7 iliustrates another variation of the shim means used in themethod of this invention.

Referring now to the figures of the drawings, a stator member l and arotor member 2 of a dynamoelectric machine are assembled in concentricrelationship, as shown in FIGURE 1, and in accordance with oneembodiment of my invention are maintained in that relationship bypreformed members 3 which are formed of an arcuate or substantiallyannular corrugated configuration and which, in effect, are used as shimsat each end of the members 1 and 2. Stator member 1' may be of thetypical variety, where a magnetic core 4 is provided with coils 5; therotor member 2 that is shown is that of a standard induction typemachine wherein a plurality of conductors 6 are short circuited togetherat each end by rings 7. Shim means 3 may be corrugated in order toachieve a spring effect, since such an arrangement facilitates theassembly of the rotor and stator with the shim means arrangedtherebetween. Of course, shim 3 could be formed of any ribbedconfiguration having a plurality of raised and depressed portions inorder to provide the desirable spring effect. As shown in FIGS. 1-4, theshim means is subtantially annular and may be of any thermoplasticmaterial, such as, for instance, a suitable polyethylene or a suitablesuperpolyamide, having a melting point sufficiently low that it isliquefied at a temperature which will not harm any other part of themachine such as, for instance, coil 5.

Rotor member 2 is generally provided with a shaft 8 securedconcentrically thereto and provided with portions 9 of decreaseddiameter which are adapted to be held within bearings, as Will be setforth below.

With the stator 1 and rotor 2 maintained in concentric relationship byshims 3, the housing of the motor, generally indicated at it isassembled to the rotor and stator assembly. Each portion 9 of the shaftis rotatably supported in a bearing 11 provided in an end shield member12, which in turn is secured to a tubular housing member 113 so as toform an enclosure for the rotor and stator. In the embodiment shown,member 13 is peripherally spaced from the outer surface of the statorcore 4 and is then secured thereto by Welding it down to the outersurface thereof, as shown at 14. It will be observed that the method ofsecuring member 13 to stator core Ii. permits the assembly to beeffected without the exercise of undue forces on the stator 1 relativeto the rotor 2, so that the shim member 3 will, in effect, determine therelative locations of the stator and rotor after assembly of theseelements into the housing 16.

While the embodiment illustrated utilizes the welded is a similar viewduring the next step of partly broken away, of the as construction shownat 14- to secure the housing member 13 to the stator core 4, it will beunderstood that the necessary feature is that means be provided toensure that the relationship of the stator and rotor to the housing willbe flexible during assembly since it is this relationship which is to bevaried instead of the concentric relationship of the'stator to therotor. Thus, for instance, the well known construction wherein bearingsare adjustably mounted in the end shields may be utilized to achievethis relationship instead of the Welded construction as shown at 14. Inaddition, any other standard means of achieving securernent of the rotorand stator to the housing assembly by relatively adjustable means may beused.

Once the assembly of the motor is complete, as shown in FIGURE 2, themotor is then arranged to be heated; that is, heat is applied, eitherdirectly or indirectly, to any of the surfaces juxtaposed to the shimmeans in order that the shim means may be melted out of the air gap.This may be effected in any desired manner, such as, for instance, thatshown in FIGURE 3 utilizing an induction coil 16. The housing of themotor is preferably provided with openings such as openings formed inend shields l2, and the motor is arranged so that when heat is appliedby the selected means, in this instance coil 16, the shim 3 ofthermoplastic material will melt and will flow out of the openings 15 asshown at 17. In this manner, the shim 3 is easily disposed of after themotor has been completely assembled without any need for exerting anykind of force on the motor or effecting any kind of disassembly thereof.Thus, the concentric relationship of the rotor 2 and the stator it,achieved by means of shims 3, is maintained after the shims have beenmelted out.

in practicing my improved method of assembling dynamoelectric machine,it will occur to those skilled'in the art that the shim means may takeother forms. For example, in FIGURES 5 and 6 the shim means isillustrated in the form of four longitudinally extending, thermoplasticmembers 3a of predetermined thickness. Obviously, the relative thicknessof the various shim members determine the uniformity of the air gapbetween the rotor and stator members. Thus, to provide concentricitybetween the rotor and stator members, the thickness of each shim member3a should be substantially the same. Although I have shown a total offour shim members 3a in FIGURE 6 as comprising the shim means, this isby way of illustration only, and it will be obvious to those skilled inthe art that the invention is not limited to a case where four shimmembers are used, but includes other variations of shim members whichserve to center the rotor within the stator member. In

certain instances, by increasing the number of shim members used, thedegree of accuracy of alignment between the rotor and stator members isaccordingly increased.

The method of assembly using shim means 3a is similar to that alreadydisclosed. initially, thermoplastic material in a plastic or semiplasticstate is applied in predetermined amounts directly to the innerperiphery 13 of the stator laminations in any suitable manner. That is,it is applied to the surface or surfaces of the stator defining thestator bore, and in the illustrated embodiment' is applied to the facesof the respective stator poles. The thermoplastic material may beextruded on to the periphery at a plurality of points, as on each pole20, and then the material, while in this plastic state, may be wiped bya suitable means to the desired thickness. After the shim means 3a hashardened to the desired degree; i.e., hardened sufficiently to hold therotor stationary relative to the stator member, the rotor 2 is insertedinto the stator ll. members then serve to position the rotor and statormem- Thus, the hardened shim bers in a predetermined, concentric, spacedrelationship,

and the assembly of the dynamoelectric machine may then be completed inthe manner heretofore described.

The final step of the assembly is, of course, to melt the shim meansthereby freeing the rotor for rotation relative to the stator.

in FIGURE 7, the shim means is shown in another variation as beingapplied to the rotor 2 instead of the inner periphery 1.8 of the stator.The shim means comprises a plurality (approximately 12) of thermoplasticmembers 3b, skewed at an angle with respect to rotor shaft 3. Of course,it is obvious that the shim means, whether preformed or applied eitherto the rotor or stator, may tune other forms than those disclosed; e.g.,helical or spiral configurations, without departure from the true spiritand scope of the invention.

It will be seen from the foregoing that this invention provides a methodof assembling a dynamoelectric machine wherein the stator and rotormembers are positively arranged in concentric relationship and aremaintained in that relationship throughout the assembly of thedynamoelectric machine, with the relationship assured even aftercomplete assembly and after the shim means have been removed.

Accordingly, it is my intention to cover all changes and modificationsof the examples of the invention herein chosen for purposes ofdisclosure, which do not constitute departures from the true spirit andscope of my invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A method of assembling a dynamoelectric machine having a stator, arotor, and a housing rigidly supporting said stator and rotatablysupporting said rotor comprising the steps of assembling said rotor andsaid stator in their predetermined concentric relationship, inserting anannular, corrugated, meltable non-metallic shim member in the air gapbetween said stator and said rotor at each end thereof to maintain themin concentric relationship with said shim member having a melting pointbelow the temperature at which temperature sensitive machine parts aredeleteriously affected, assembling said stator and rotor in saidhousing, securing said stator and housing together while maintainingsaid corrugated meltable shim members in said air gap, and applying heatto the assembled dynamoelectric machine to liquefy said shim members andcausing said liquefied shim members to be removed from said air gap torelease said stator and said rotor relative to each other, said housingfixedly retaining said predetermined concentric relationship establishedby said corrugated shim members.

2. A method of assembling a dynamoelectric machine having a stator, arotor, and frame means securing together said stator and rotatablysupporting said rotor for relative rotation, comprising the steps ofassembling said rotor and said stator in a predetermined spacedrelationship to define an air gap therebetween-with'solid fluidic shimmeans of non-metallic material disposed in the air gap engaging therotor and said stator with said shim means having a point of fluiditybelow the temperature at which temperature sensitive machine parts aredeleteriously affected, assembling said rotor and said stator with saidframe means while said fluidic shim means maintains said predeterminedrelationship betweenthe rotor and stator, and applying heat to the shimmeans of the assembled dynamoelectric machine to fiuidize said shimmeans and causing the fluidicmaterial'to be removed in fluid form fromsaid air gap for releasing said rotor and said stator for relativerotation,-said frame means retaining said predetermined relationshipestablished by the solid fiuidic material.

3. A method of assembling a dynamoelectric machine having a statormember, a rotor member, and a frame assembly supporting said members forrelative rotation with an air gap provided therebetween comprising thesteps: applying non-metallic fusible'rnaterial in an unhardened stateonto the surface of at least one of said members and forming thematerial into shim means of predetermined thickness on said surface, thefusible material having a point of fusion below the temperaturesensitive machine parts are deleteriously affected; hardening said meansto the degree necessary for maintaining said members temporarilystationary in a predetermined spaced relationship; arranging said rotorand stator members in a predetermined spaced relationship with saidhardened shim means in said air gap to hold said members temporarily insaid relation; securing said frame assembly and stator member togetherwhile said hardened fusible shim means maintains said predeterminedrelationship between the rotor and stator members, and causing thefusible material to be removed in fluid form from the air gap forreleasing said stator and rotor members relative to each other, saidframe assembly fixedly retaining said predetermined spaced relationshipestablished by said hardened fusible shim means.

4. A method of assembling a dynamoelectric machine having a statormember formed with a surface defining a rotor receiving bore, a rotormember, and a housing assembly supporting said members for relativerotation and in a spaced concentric relationship to define a uniform airgap therebetween comprising the steps: applying non-metallic fusiblematerial in an unhardened state onto the surface of at least one of saidmembers at a number of angularly spaced apart positions, with saidfusible material having a fusion point below the temperature at whichthe temperature sensitive machine parts are deleteriously affected andwiping said material to produce a plurality of elongated transverselyarcuate shaped shims of substantially the same thickness adhering tosaid surface, with each shim being generally uniform in thicknessthroughout its length; hardening the shims to the degree necessary tomaintain said members temporarily in the predetermined concentricrelationship; assembling said rotor and stator members in said spacedconcentric relationship with the hardened shims disposed in the air gapand in engagement with the peripheral surface of the other member;securing said housing assembly and stator member rigidly together withthe housing assembly supporting said rotor member while said shimsmaintain said members in the predetermined concentric relationship; andapplying sufi'icient heat to said shims to fluidize them and causing theshims to be removed from the air gap, the stator and rotor members beingreleased for relative rotation and the predetermined concentricrelationship established by the shims being fixedly retained by saidhousing assembly.

5. A method of assembling a dynamoelectric machine having a stator, arotor, and frame means securing together said stator and rotatablysupporting said rotor for relative rotation, comprising the steps ofassembling said rotor and said stator in a predetermined spacedconcentric relationship to define an air gap therebetween with shimmeans of hardened non-metallic thermoplastic material disposed in theair gap engaging said rotor and said stator, said shim means having apoint of liquifaction below the temperature at which the temperaturesensitive machine parts are deleteriously affected, assembling saidrotor and said stator with said frame means, securing said stator andframe means together while said hardened shim means maintains saidpredetermined concentric relationship between the rotor and stator, andapplying heat to the shim means of the assembled dynamoelectric machineto liquefy said shim means and causing said liquid shim means to flowfrom said air gap for releasing said stator and said rotor relative toeach other, said frame means retaining the predetermined relationshipestablished by said hardened shim means.

References Cited by the Examiner UNITED STATES PATENTS 1,527,162 2/25Alvord 29-155.59 X 2,423,750 7/47 Benson.

2,476,937 7/49 White 1176 2,608,529 8/52 Varian 29423 X 3,002,261 10/61Avila et al. 29-1555 WHITMORE A. WILTZ, Primary Examiner. JOHN F.CAMPBELL, Examiner.

1. A METHOD OF ASSEMBLYING A DYNAMOELECTRIC MACHINE HAVING A STATOR, AROTOR, AND A HOUSING RIGIDLY SUPPORTING SAID STATOR AND ROTATABLYSUPPORTING SAID ROTOR COMPRISING THE STEPS OF ASSEMBLING SAID ROTOR ANDSAID STATOR IN THEIR PREDETERMINED CONCENTRIC RELATIONSHIP, INSERTING ANANNULAR, CORRUGATED, MELTABLE NON-METALLIC SHIM MEMBER IN THE AIR GAPBETWEEN SAID STATOR AND SAID ROTOR AT EACH END THEREOF TO MAINTAIN THEMIN CONCENTRIC RELATIONSHIP WITH SAID SHIM MEMBER HAVING A MELTING POINTBELOW THE TEMPERATURE AT WHICH TEMPERATURE SENSITIVE MACHINE PARTS AREDELETERIOUSLY AFFECTED, ASSEMBLING SAID STATOR AND ROTOR IN SAIDHOUSING, SECURING SAID STATOR AND HOUSING TOGETHER WHILE MAINTAININGSAID CORRUGATED MELTABLE SHIM MEMBERS IN SAID AIR GAP, AND APPLYING HEATTO THE ASSEMBLED DYNAMOELECTRIC MACHINE TO LIQUEFY SAID SHIM MEMBERS ANDCAUSING SAID LIQUEFIED SHIM MEMBERS TO BE REMOVED FROM SAID AIR GAP TORELEASE SAID STATOR AND SAID ROTOR RELATIVE TO EACH OTHER, SAID HOUSINGFIXEDLY RETAINING SAID PREDETERMINED CONCENTRIC RELATIONSHIP ESTABLISHEDBY SAID CORRUGATED SHIM MEMBERS.